J R Gaunt & Son started in Birmingham, England in 1870 and they made a variety of buttons all the way until 1973. From 1884 to 1899 they made button in London under the same name with some buttons later saying sons instead of son, but used both variations, therefore my guess is your button was made between 1884 and 1899.
The reason I make the aforementioned statement regarding the date is because in 1899 they changed the name of the companies mark to J R Gaunt & Sons LTD and used this name from 1891 until 1991. Also during the same time period the name varied depending on the button, I suppose. They used the name, J R Gaunt & Sons LTD ENG, J R Gaunt & Sons LTD London ENGLD and J R Gaunt & Sons London England. After the 1900 the companies mark was J R Gaunt & sons LTD NY & London... Sorry for rambling about Gaunt, but the list goes on, however I'll give it a break... LOL
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